It requires a long time to know anyone.
The wise hand does not all the tongue dictates.
From reading too much, and sleeping too little, his brain dried up on him and he lost his judgment.
Pray, look better, sir... those things yonder are no giants, but windmills.
Do you see over yonder, friend Sancho, thirty or forty hulking giants? I intend to do battle with them and slay them.
Don't put all your eggs in one basket.